﻿// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Generic;

namespace AvaloniaEdit.Rendering
{
    /// <summary>
    /// Base class for <see cref="IVisualLineTransformer"/> that helps
    /// splitting visual elements so that colors (and other text properties) can be easily assigned
    /// to individual words/characters.
    /// </summary>
    public abstract class ColorizingTransformer : IVisualLineTransformer, ITextViewConnect
    {
        /// <summary>
        /// Gets the list of elements currently being transformed.
        /// </summary>
        protected IList<VisualLineElement> CurrentElements { get; private set; }

        /// <summary>
        /// <see cref="IVisualLineTransformer.Transform"/> implementation.
        /// Sets <see cref="CurrentElements"/> and calls <see cref="Colorize"/>.
        /// </summary>
        public void Transform(ITextRunConstructionContext context, IList<VisualLineElement> elements)
        {
            if (CurrentElements != null)
                throw new InvalidOperationException("Recursive Transform() call");
            CurrentElements = elements ?? throw new ArgumentNullException(nameof(elements));

            try
            {
                Colorize(context);
            }
            finally
            {
                CurrentElements = null;
            }
        }

        /// <summary>
        /// Performs the colorization.
        /// </summary>
        protected abstract void Colorize(ITextRunConstructionContext context);

        /// <summary>
        /// Changes visual element properties.
        /// This method accesses <see cref="CurrentElements"/>, so it must be called only during
        /// a <see cref="Transform"/> call.
        /// This method splits <see cref="VisualLineElement"/>s as necessary to ensure that the region
        /// can be colored by setting the <see cref="VisualLineElement.TextRunProperties"/> of whole elements,
        /// and then calls the <paramref name="action"/> on all elements in the region.
        /// </summary>
        /// <param name="visualStartColumn">Start visual column of the region to change</param>
        /// <param name="visualEndColumn">End visual column of the region to change</param>
        /// <param name="action">Action that changes an individual <see cref="VisualLineElement"/>.</param>
        protected void ChangeVisualElements(int visualStartColumn, int visualEndColumn, Action<VisualLineElement> action)
        {
            if (action == null)
                throw new ArgumentNullException(nameof(action));
            for (int i = 0; i < CurrentElements.Count; i++)
            {
                VisualLineElement e = CurrentElements[i];
                if (e.VisualColumn > visualEndColumn)
                    break;
                if (e.VisualColumn < visualStartColumn &&
                    e.VisualColumn + e.VisualLength > visualStartColumn)
                {
                    if (e.CanSplit)
                    {
                        e.Split(visualStartColumn, CurrentElements, i--);
                        continue;
                    }
                }
                if (e.VisualColumn >= visualStartColumn && e.VisualColumn < visualEndColumn)
                {
                    if (e.VisualColumn + e.VisualLength > visualEndColumn)
                    {
                        if (e.CanSplit)
                        {
                            e.Split(visualEndColumn, CurrentElements, i--);
                        }
                    }
                    else
                    {
                        action(e);
                    }
                }
            }
        }

        /// <summary>
        /// Called when added to a text view.
        /// </summary>
        protected virtual void OnAddToTextView(TextView textView)
        {
        }

        /// <summary>
        /// Called when removed from a text view.
        /// </summary>
        protected virtual void OnRemoveFromTextView(TextView textView)
        {
        }

        void ITextViewConnect.AddToTextView(TextView textView)
        {
            OnAddToTextView(textView);
        }

        void ITextViewConnect.RemoveFromTextView(TextView textView)
        {
            OnRemoveFromTextView(textView);
        }
    }
}
